Adverse maternal outcomes and associated factors among mothers of advanced age delivering at a tertiary hospital, southwestern Uganda: a cross-sectional study

Background Mothers of advanced age, defined as pregnant women aged ≥ 35 years at the time of giving birth, are traditionally known to be associated with increased risks of adverse maternal outcomes. We determined the prevalence of adverse maternal outcomes and associated factors among mothers of advanced age who delivered at Kabale Regional Referral Hospital (KRRH), in Southwestern Uganda. Methods We conducted a cross-sectional study at the Maternity Ward of KRRH from April to September 2023. We consecutively enrolled pregnant women aged ≥ 35 years during their immediate post-delivery period and before discharge. We obtained data on their socio-demographic, obstetric, medical characteristics and their maternal outcomes using interviewer-administered questionnaires. We defined adverse maternal outcome as any complication sustained by the mother that was related to pregnancy, delivery and immediate post-partum events (obstructed labour, antepartum haemorrhage, mode of delivery [cesarean or vacuum extraction], postpartum haemorrhage, hypertensive disorders of pregnancy, preterm or postdate pregnancy, anemia, premature rupture of membranes, multiple pregnancy, and maternal death). A participant was considered to have an adverse outcome if they experienced any one of these complications. We identified factors associated with adverse outcomes using modified Poisson regression. Results Out of 417 participants, most were aged 35–37 years (n = 206; 49.4%), and had parity ≥ 5 (65.5%). The prevalence of adverse maternal outcomes was 37.6% (n = 157, 95%CI: 33.1–42.4%). Common adverse maternal outcomes included caesarian delivery (23%), and obstructed labour (14.4%). Other complications included anemia in pregnancy (4.5%), chorioamnionitis (4.1%), preterm prelabour rupture of membranes (3.9%), and chronic hypertension and preeclampsia (both 2.4%). Factors associated with adverse maternal outcomes were precipitate labour (adjusted prevalence ratio [aPR] = 1.95, 95%CI: 1.44–2.65), prolonged labour, lasting > 12 h (aPR = 2.86, 95%CI: 1.48–3.16), and chronic hypertension (aPR = 2.01, 95%CI: 1.34–3.9). Conclusion Approximately two-fifth of the advanced-aged mothers surveyed had adverse outcomes. Mothers with prolonged labour, precipitate labour and chronic hypertension were more likely to experience adverse outcomes. We recommend implementation of targeted interventions, emphasizing proper management of labor as well as close monitoring of hypertensive mothers, and those with precipitate or prolonged labor, to mitigate risks of adverse outcomes within this study population.


Introduction
Advanced aged mothers refer to those mothers aged 35 years or older during pregnancy or childbirth [1].Globally, there is an observable trend of an increasing average age at childbearing [2,3].This shift is facilitated by the widespread adoption of assisted reproductive technology, extending to menopausal women through egg donor programs.Contributing factors to this trend include intentional delays due to career commitments, prolonged professional paths, postponed marriages, and the continuation of childbearing into later stages of life [4].
Factors associated with adverse pregnancy outcomes among mothers of advanced age include chronic medical conditions such as diabetes and hypertensive disease, parity, socio-demographic factors such as maternal age, level of education and income and labor duration.[5,[11][12][13].Maternal age has been independently associated with adverse outcomes with those beyond 40 years experiencing a higher impact [3,10,13].
In Southwestern Uganda, there is a gap in understanding maternal outcomes and associated factors among advanced-aged mothers, as no previous study has addressed this issue.The current study aims to fill this gap by laying the groundwork for evidence-based preventive interventions tailored to mothers in this age group.The findings do not only aim to improve outcomes, but also establish a framework for future research specific to this maternal demographic.Specifically, this study determined the prevalence of adverse maternal outcomes and associated factors among advanced-aged mothers receiving care at a tertiary hospital in southwestern Uganda.

Study setting, study design and study population
We conducted a cross sectional study at the Maternity Ward of Kabale Regional Referral Hospital (KRRH) in Southwestern Uganda.The hospital doubles as a teaching hospital for Kabale University School of Medical as well as a regional referral hospital for districts in southwestern Uganda and neighbouring countries of Democratic Republic of Congo and Rwanda.The Maternity Ward of the hospital conducts approximately 450 deliveries every month, with a caesarean section rate of 18-20%.
We included in our study all mothers aged 35 years and older during their immediate post-delivery period and before discharge who were admitted from March to August 2023.

Sample size and sampling methods
The sample size(n) was calculated using the Kish-Leslie formula [14] with a 5% significance level and 95% confidence level: where: n is the total number of participants required.z is the critical value (it is 1.96 at 0.05 level of significance).
Accounting for a 10% non-response rate, a total sample size of 427 was obtained as shown below:

Data collection and study variables
Data were collected using interviewer administered structured questionnaires after obtaining written informed consent by four trained research assistants.These were midwives closely supervised by the principal investigator.We collected data on independent variables n = (z 2 pq) Maternal adverse outcomes were obstructed labour, antepartum haemorrhage, mode of delivery (vacuum extraction or cesarean delivery), postpartum haemorrhage, hypertensive disorders of pregnancy, gestational age at delivery (preterm or postterm), anemia, premature rupture of membranes, multiple pregnancy, and maternal death.We defined adverse maternal outcomes as any of above complications sustained by the mother related to the most recent pregnancy, delivery and immediate postpartum events.

Data management and analysis
Data was entered in Epi Info software version 7 (CDC, Atlanta, USA) and exported to STATA version 15 (Stata-Corp, College Texas, USA) for analysis.
Maternal socio-demographic, obstetric, medical characteristics and fetal outcomes were summarized using descriptive statistics and expressed as frequencies/ percentages.To determine the prevalence of adverse maternal outcomes, we calculated the percentage of participants experiencing any one of the complications related to pregnancy, delivery, and immediate post-partum events over the total study participants.
For both bivariate and multivariate analyses, we used a generalized linear model regression of the Poisson family with a log link (modified Poisson), with robust standard errors to identify factors associated with adverse outcomes among the study participants.This is because the prevalence of our outcome of interest was high [15,16].Variables meeting a significance threshold of p-value < 0.2 at bivariate analysis and those with biological plausibility, such as maternal age, were retained in the multivariable regression model.We reported prevalence ratios and their corresponding confidence intervals as measures of association.Significance for all analyses was set at p < 0.05.

Results
Out of 2,700 mothers who delivered during the study period of six months, 436(16.1%)were of advanced age.Three mothers declined consent to participate while other sixteen went home before completing questionnaires.We enrolled 417 women who were eligible to participate (Fig. 1).

Demographic, obstetric and medical characteristics of the study participants
Among the 417 participants, most fell within the age range of 35-37 years (49.4%),followed by those aged 38-40 years (36.9%), while only 13.7% were above 40 years old.Educational attainment was predominantly at the primary or secondary level (36.9% and 37.2%, respectively).A significant proportion were married (87.5%), resided in rural areas (65.7%), and were multiparous with five or more previous pregnancies (65.5%).The majority attended at least four antenatal care (ANC) visits (94%) and utilized contraception between pregnancies Fig. 1 Flow chart for recruitment of study participants (77.9%).Chronic illnesses were reported in 3.3% of participants (Table 1).

Discussion
In this study, approximately two in five of the advanced aged mothers surveyed experienced at least one adverse maternal outcome.The most common adverse outcomes among these mothers were caesarian delivery and obstructed labour.Advanced aged mothers with prolonged labour, precipitate labour and chronic hypertension were more likely to experience adverse outcomes.
The overall rate of adverse maternal outcomes in the current study was 37.6%.This compares well with study findings from other countries such as 32.1% in Ethiopia [6], 36% in Israel [9,17], 37.5% in Spain [18] and 36% in the USA [11].However, the rate of adverse maternal outcomes in the current study was lower than the rates reported in Poland, Brazil, the USA, and Israel, where studies documented a higher proportion of mothers experiencing adverse outcomes ranging from 38 to 56% study [3,[19][20][21].This divergence in adverse maternal outcome rates between our study and those in Poland, Brazil, the USA, and Israel can be attributed to the substantial inclusion of participants aged above 40 years in those studies.Advanced maternal age, especially beyond 40 years, is widely recognized as a significant risk factor for adverse outcomes, as corroborated by previous research [3].Conversely, our study had a limited number of mothers aged 40 years or older, likely contributing to a lower proportion of adverse outcomes observed.Moreover, the comparatively favorable outcomes in our study may be attributed to several protective factors prevalent among our participants; the majority (94%) benefited from adequate antenatal care, minimizing potential complications.Additionally, the low prevalence of chronic medical morbidities among our study population and the widespread use of contraception likely contributed to the observed lower rate of adverse maternal outcomes compared to these studies.Furthermore, a significant proportion of our participants had achieved a fairly high level of education, which is consistently associated with improved maternal health outcomes [22].
In the current study, having prolonged or precipitate labour was associated with adverse outcomes among participants.Abnormal labour duration is consistently associated with maternal morbidities such as operative delivery, postpartum haemorrhage and sepsis [24].Therefore, we recommend proper labor monitoring among advanced-aged mothers to avoid undue prolongation by intervening timely.In case these mothers experience precipitate labour, close and vigilant monitoring as well as prompt management of associated adverse outcomes should be considered as essential components of comprehensive care for this population.
In this study, having chronic hypertension was also associated with adverse maternal outcomes, consistent with other studies in the USA and the UK [25,26].This is because such mothers are faced with a high likelihood of elective operative delivery, gestational diabetes, and preeclampsia or eclampsia.On the basis of this finding, we recommend that advanced aged mothers with chronic hypertension be closely monitored during pregnancy, labour and delivery to avoid and or manage associated adverse outcomes.
This study is subject to certain limitations that merit acknowledgment.One notable constraint arises from the relatively modest sample size within the study group aged 40 years or older; restricting our statistical power to comprehensively assess the influence of very advanced maternal age on adverse perinatal outcomes.Women aged 40-44 years are known to be at more increased risk for adverse outcomes compared with women aged 35-39 years [23].Additionally, the absence of a cohort of younger mothers for comparative analysis presents a limitation, as the entirety of our study participants were aged 35 years or older.Finally, our study findings are generalizable to advanced-aged women in the Southwestern Uganda region and similar peri-urban sub-Saharan African settings, and may not be generalizable to other study settings or populations.Despite these limitations, the primary strength of our study lies in its pioneering nature as one of the first investigations to explore adverse maternal outcomes among advanced-aged mothers in the East African Region.

Table 1
Demographic, obstetric and medical characteristics of the participants (N = 417)

Table 2
Maternal outcomes of study participants (N = 417)

Table 3
Factors associated with adverse maternal outcomes among mothers of advanced age at Kabale Regional Referral Hospital, southwestern Uganda Approximately two in five of the advanced-aged mothers surveyed had adverse outcomes.The most common adverse outcomes among these mothers are caesarian delivery and obstructed labour.Mothers with prolonged labour, precipitate labour and chronic hypertension are more likely to experience adverse outcomes compared to their counterparts.We recommend implementation of targeted interventions, emphasizing proper management of labor, close monitoring of advanced aged mothers, and a deliberate effort to avoid prolonged, to mitigate risks of adverse outcomes within this study population.In case of precipitate labour, such mothers should be closely monitored for adverse outcomes and timely interventions.Mothers conceiving or intending to conceive at advanced age should be counselled about likelihood of the adverse outcomes.Future longitudinal studies are recommended to better understand the immediate and long-term maternal outcomes associated with advanced maternal age in our setting.
aPR Adjusted prevalence ratio, cPR Crude prevalence ratio, CI Confidence interval, Ref Reference category Conclusion